# Observation of the $\Lambda_b^0\rightarrow J/\psi p \pi^-$ decay

LHCb Collaboration; Bernet, R; Müller, K; Steinkamp, O; Straumann, U; Serra, N; Vollhardt, A; et al (2014). Observation of the $\Lambda_b^0\rightarrow J/\psi p \pi^-$ decay. Journal of High Energy Physics, 2014(103):online.

## Abstract

The first observation of the Cabibbo-suppressed decay $\Lambda_b^0\rightarrow J/\psi p \pi^-$ is reported using a data sample of proton-proton collisions at 7 and 8 TeV, corresponding to an integrated luminosity of 3 $\rm fb^{-1}$. A prominent signal is observed and the branching fraction relative to the decay mode $\Lambda_b^0\rightarrow J/\psi p K^-$ is determined to be $$\frac{{\cal B}(\Lambda_b^0\rightarrow J/\psi p \pi^-)}{{\cal B}(\Lambda_b^0\rightarrow J/\psi p K^-)}=0.0824\pm0.0025\:(\text{stat})\pm0.0042\:(\text{syst}).$$ A search for direct CP violation is performed. The difference in the CP asymmetries between these two decays is found to be $${\cal A}_{CP}(\Lambda_b^0\rightarrow J/\psi p \pi^-)-{\cal A}_{CP}(\Lambda_b^0\rightarrow J/\psi p K^-)=(+5.7\pm 2.4\:(\text{stat})\pm1.2\:(\text{syst}))\%,$$ which is compatible with CP symmetry at the $2.2\sigma$ level.

## Abstract

The first observation of the Cabibbo-suppressed decay $\Lambda_b^0\rightarrow J/\psi p \pi^-$ is reported using a data sample of proton-proton collisions at 7 and 8 TeV, corresponding to an integrated luminosity of 3 $\rm fb^{-1}$. A prominent signal is observed and the branching fraction relative to the decay mode $\Lambda_b^0\rightarrow J/\psi p K^-$ is determined to be $$\frac{{\cal B}(\Lambda_b^0\rightarrow J/\psi p \pi^-)}{{\cal B}(\Lambda_b^0\rightarrow J/\psi p K^-)}=0.0824\pm0.0025\:(\text{stat})\pm0.0042\:(\text{syst}).$$ A search for direct CP violation is performed. The difference in the CP asymmetries between these two decays is found to be $${\cal A}_{CP}(\Lambda_b^0\rightarrow J/\psi p \pi^-)-{\cal A}_{CP}(\Lambda_b^0\rightarrow J/\psi p K^-)=(+5.7\pm 2.4\:(\text{stat})\pm1.2\:(\text{syst}))\%,$$ which is compatible with CP symmetry at the $2.2\sigma$ level.

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Item Type: Journal Article, refereed, original work 07 Faculty of Science > Physics Institute 530 Physics Physical Sciences > Nuclear and High Energy Physics English 2014 24 Feb 2015 09:57 07 May 2020 00:00 Springer 1029-8479 Gold https://doi.org/10.1007/JHEP07(2014)103